Audio Tone Details
Edit on GitHubThe exact tone map: SEARCH pitch progression, Morse clicks and the EMERGENCY tone
Audio Tone Details
Overview
Audio is a single-wire system on GPIO 25 with distinct tones per context. Understanding the tone map tells you what the beacon is doing without looking at it.
Tone Map
| Context | Frequency | Meaning |
|---|---|---|
| SEARCH, no signal | Silence (parked) | Below threshold |
| SEARCH, WEAK | 440 Hz rising | Signal near threshold |
| SEARCH, MEDIUM | ~880 Hz | Getting stronger |
| SEARCH, STRONG | Up to 2200 Hz | Very strong signal |
| BEACON TX | 600 Hz clicks | Morse keying |
| EMERGENCY | 1760 Hz continuous | Emergency mode |
Pitch Linearization
In SEARCH, pitch is mapped linearly from the RSSI:
- At exactly the threshold: 440 Hz.
- At -60 dBm: ~880 Hz.
- At -40 dBm and above: ~2200 Hz.
The rising pitch with rising signal is the “metal detector” feel.
Why 600 Hz Clicks in BEACON
Morse keying is a square wave of on/off; 600 Hz inside each element makes each dot/dash audible as a short tone burst. This is the audio confirmation of RF keying.
Volume and Targets
- Default volume 180 (~70%), range 0-255.
- SW_UP/DN adjust the selected target (VOL or WPM).
- Hold SEL 1 s to persist.